Empty threat (5,5)
I believe the answer is:
paper tiger
'empty threat' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for paper tiger that I've seen before include "Threatening person that is really ineffectual" , "One misleadingly appearing threatening" , "Something appearing threatening but actually ineffectual" , "One not as fierce as seems" , "empty threat" .)